9 Claims. (Cl. 252-99) The reaction is exothermic and since sodium hydrochlorite decomposes at elevated temperatures of the order of 150 F., reaction temperature control and removal of water of reaction have presented problems.

It has now been found that a stable, solid chlorinated caustic product having an vailable chlorige conftem,of aup to abgyt 1 can,.be prepared by chlorinating under articular chlorination conditions an admixture of sodium hydroxide with anhydrous hygroscopic complex sodium phosphates, such as sodium pyrophosphate and sodium tripolyphosphate, or sodium metasilicate, or mixtures thereof, in defined proportions.

According to this invention, a finely divided solid reaction mixture containing sodium hydroxide and a hygroscopic material which is an anhydrous complex sodium phosphate, sodium metasilicate, or a mixture thereof, is contacted with a gas stream containing sufficient chlorine to initiate an exothermic reaction at atmospheric or slightly elevated pressures. The weight ratio of caustic to hygroscopic material in the finely divided solid reaction mixture is about 1 to 9:1 respectively, advantageously 1.5 to 4:1. The gas stream containing chlorine is reacted with the solid reaction mixture while maintaining the reaction temperature within the range from about 110 to 140 F., preferably 120 to 130 F., until the available chlorine content of the solid reaction mixture is about 8 to 18%, preferably 14 to 16%. The reaction temperature is then increased to about 135 to 160 F., preferably 140 to 150 F., for a reaction period of at least about 10 minutes but insufficient to decrease the available chlorine content of the solid reaction mixture by more than about 2%. The chlorination reaction is then terminated and the reaction mixture is cooled.

The caustic is advantageously sized to pass about number 10 sieve (US. Standard Screen) and the hygroscopic material is advantageously similarly sized. A typical screen analysis is 0% on #10, 20% on #20, 50% on #30, 25% on #40 and on #50. The chlorination reaction appears to take place on the caustic surface and when employing such a sized reaction mixture, a more homogeneous product is obtained.

The anhydrous complex sodium phosphate and/or sodium metasilicate serve to take up water formed and control the chlorination reaction. During the higher temperature portion of the chlorination reaction, they also appear to fuse and/or coalesce with the chlorinated caustic so that a product of unusual stability with respect to available clorine is obtained. In general, the greater EXAMINER 3,166,512 Patented Jan. 19, 1965 the proportion of the hygroscopic material in the solid reaction mixture, the slower will be the rate of chlorination. Hence, weight proportions of caustic to hygroscopic material of less than about 1:1 respectively lead 5 to impracticably slow chlorination rates. In order to obtain products of high available chlorine stability, however, it has been found that weight proportions of caustic to hygroscopic material of greater than about 9:1 respectively cannot be employed. The optimum weight proportion of caustic to hygroscopic material with respect to both chlorination rate and available chlorine stability appears to be about 2.3:1 respectively.

The chlorination reaction temperature can be controlled by employing a chlorination gas stream diluted with air or other inert gas, such as nitrogen, which advantageously has been pre-dried. The proportion of chlorine in the gas stream is at first relatively high to initiate the exothermic chlorination reaction and then is reduced to maintain the reaction temperature at the required level. The reaction temperature can be increased for the higher temperature portion of the reaction by increasing the proportion of chlorine in the gas stream. Advantageously at the completion of the chlorination reaction, cooling is accomplished at least in part by the gas stream in which the proportion of chlorine is relatively low.

The reaction can be carried out in any type of apparatus suitable for gas-solid type reactions. A convenient apparatus is a conventional drum-dryer containing internal bafiles and equipped with heat removal means, for ex- 30 ample, means for spray cooling, or internal or external cooling coils for removing the exothermic heat of reaction, and means for introducing and recovering and recycling the chlorine. The apparatus employed, however, should provide for intimate mixture of the gases and solids and, in addition, should provide for agitation of the solids throughout the reaction and subsequent cooling such that agglomeration does not occur and the solid reaction mixture is at all times maintained in the form of finely divided discrete particles.

The process of this invention is illustrated in detail by the following examples. The apparatus employed in Examples 1 to 8 was a rotating drum 23 inches in diameter and 35 inches long equipped with internal bafiles, a gas inlet at one end connected with a perforated tube as an axis and a gas vent at the other end. The drum rotated at about 15-20 r.p.m. The drum was wrapped with cloth and means were provided for spraying the cloth with water and for subjecting the cloth to a forced air draft to effect cooling by evaporation.

sodium tripolyphosphate. The US. Standard Screen analysis of the reactants was as follows:

Rotation was started and chlorine gas was introduced from a cylinder into the drum at the rate of 20 liters per minute (measured at 20 C.). In about 15 minutes, the temperature of the reaction mixture had risen to about 110 F. and the introduction of dry air into the chlorine gas stream was begun. The amount of air 1ntroduced was varied between to 3 liters per minute (measured at 20 C.) and the amount of chlorine introduced was (measured at 20 C.) and the amount of chlorine introduced was varied between 1 to 3 liters per minute (measured at 20 (1.). Variation of the gas stream composition and flow rate together with the water spray on 0 liters r minute (measured 5 the drum maintained the temperature of the reaction 3 2?" gy l dr iaii rl if the gzfs stream composition mixture at about 115 to 135 F. These conditions were and flow rate together with the wet cloth wrapping mainmamtamed for two hours at the end of which period the tained the temperature of the reaction mixture at about air flow and the chlorine flow rate were ad usted to 120-130 F. After about two hours, samples of the provide a reaction m1xture temperature of about 140 F. solid reaction i e wgre k n periodically and titrated for an additlonal period of 30 minutes. The react on for available chlorine. At the end of about 4 hours the mixture was then cooled with an air stream contain ng available chlorine content of the solid reaction mixture a small amount of chlorine. The final available chlorine was The air flow to the drum and the forced air content of the reaction mixture was 16.5%. draft to the drum wrapping were cut off and the chlor ne 15 EXAMPLE 10 r em ra ure rion fi l tlh e l eaflio nl 'l h i i mgsal ifig rtrse t 140 in 3 Into the laboratory s1ze drum were placed 240 grams few minutes and was maintained at 140-145 F. for 15 of Sodium hydroxide 1n the form of ground flakes with utes The solid reaction mixture appeared slightly a screen analysis as EXaIPPle 1 and grams 9 anhy' 3:; d began to simer At the end of the 15 minute drous technical grade sodium IIlCiaSlllCflie hav1ng the p g the chlorine flow was reduced to 1 liter per following U.S. Standard Screen analys1s: minute, the air flow was set at 2 liters per minute, and s p m f rg d air draft to the drum wrapper was t n on 20 0.2 in order to cool the solid reaction mixture to about 03 h gas stream was then cut off. the d 7.6 stopped and the product removed. 25 6O 10.5 A t t l f 13 pounds of chlorine was intr d mm 20.7 h d m during the reaction and about 3 10 4 Pounds 1 14.3 reacted. The bulk of the final product had increased Pan 464 75 to 1 during f Teacnon- The Product was P 30 The reaction was carried out in essentially the same relatively fine y dlvlded however: 50% Passmg manner as described in Example 9, the pertinent data through a 20 mesh screen. The avallable chlorine conappearing in Table II following. tent of the final product was about 14%.

The pertinent data from this and other runs are shown EXAMPLE 11 in the following Table 1. Into the laboratory size drum were placed 225 grams Table l Chlorine Air Initial Initial Final Final Final Example Rate, Rate, Reaction Reaction Reaction Reaction Available No. l./min. l./min. Temperature, Time, Temperature, Time, Chlorine,

F. hours F. Min. Percent Additional experiments were carried out in a laboraof sodium hydroxide in the form of ground flakes with tory size apparatus which included a Plexiglas drum a screen analysis as in Example 1, 37.5 grams anhydrous about six inches in a diameter and a foot long rota-ting technical grade powdered sodium pyrophosphate and at a speed of about 20 to 30 rpm. The axle upon which 37.5 grams anhydrous technical grade granular sodium the drum rotated was perforated and open at one end pyrophosphate having the following U.S. Standard Screen for introduction of chlorine and air. The drum was 00 analysis: cooled by a spray of water directed on its top and collected in a tray below.

EXAMPLE 9 SW 5. 35551% 5.521511 Into the drum were placed 240 grams of sodium hydroxide in the form of ground flakes with a screen Tracg g g analysis as in Example 1 and 60 grams of sodium tri- Q1 1 polyphosphate (anhydrous) with a screen analysis as in 2% 5% Example 1. Rotation was started and chorine gas from 3211 11s a cylinder was introduced into the drum at the rate of 112 3 liters per minute (measured at 20 C.). In about 10 minutes the temperature of the reaction mixture had risen to about 115 F. and the introduction of dry air into the chlorine gas stream was begun. The amount of air introduced was varied between 0 to 3 liters per minute The reaction was carried out in essentially the same manner as described in Example 10, the pertinent data appearing in Table II following.

Storage stability tests were performed with certain of the products shown in Table I. In these tests, the available chlorine content of the product was determined immediately prior to the test, about 10 gram samples of the product were placed in small clear glass bottles closed with a screw cap, and the bottles stored in a dark storage cabinet. At the conclusion of the test, the bottle was removed from the storage cabinet and its available chlorine content was again determined. A portion of the product of Example 7 was first screened on a No. 20 mesh screen. The particles remaining on the screen were designated 7A and those passing through the screen were designated 7B. The pertinent data appear in Table HI below.

As shown in Table III, the stability of the products made in the laboratory reactor are not as stable as those made in the larger pilot plant reactor employed in Examples 1-8 apparently because of inadequate tumbling action during the second reaction sintering stage.

Another aspect of this invention relates to stable solid, detergent formulations containing the chlorinated caustic product, which formulations are of particular value in machine dishwashing.

Machine dishwashing is used in connection with practically all commercial and institutional dining facilities as well as in a rapidly increasing proportion of private homes. It has been the practice in formulating machine dishwashing detergents to use in the main various combinations of inorganic sodium and potassium salts, such as polyphosphates, silicates, carbonates and basic materials such as sodium and potassium hydroxides. It has been recognized that detergency would be enhanced and that germicidal and destaining properties would be imparted to detergent formulations by incorporation therein of available chlorine containing solid components. Thus, formulations containing chlorinated trisodium phosphate and trichlorocyanuric acid have been prepared and have proven entirely satisfactory for some purposes.

Chlorinated trisodium phosphate must, however, be formulated with hydrated salts for best stability and since it contains only about 3.5% available chlorine, formulation flexibility is reduced. In addition, the orthophosphate present when cholrinated trisodium phosphate is employed in machine dishwashing formulations tends to film glassware. Also, trichlorocyanuric acid containing detergents, when used in machine dishwashing formulations, releases gaseous chlorine in conventional detergent reservoirs and this is objectionable in some instances. More important, however, for heavy duty formulations, i.e., those requiring caustic, the presently available chlorinated solids cannot be employed because they are not compatible with the alkali metal hydroxides.

The chlorinated caustic products of this invention, on the other hand, can be formulated with anhydrous salts, giving a more concentrated finished product, provide increased formulation flexibility due to their high available chlorine content, and are compatible with the alkali metal hydroxides.

Advantageously, the detergent formulations of this invention contain sufficient chlorinated caustic to provide from about 0.5 to 8% available chlorine in the finished composition. In addition to the chlorinated caustic, which imparts germicidal and destaining properties, the detergent compositions of this invention contain alkaline salts which are conventionally employed to perform three essential functions: (1) condition the water so that the detersive action can take place more effectively; (2) remove the soil from the dishes thoroughly, completely and rapidly; and (3) leave the dish surface in a state where the water drains in a continuous film without breaking into little hanging drops or streams and without leaving objectionable residues. Many of the alkaline salts act as both water conditioners and soil removers but will be discussed on the basis of their primary function.

Sodium carbonate, although it is among the least effective water-conditioning agents, together with its sesquicarbonate, is almost universally used as a component in dishwashing compounds, because of its low cost. The detergent compositions of this invention can contain from 0 to 50% by weight of sodium or potassium carbonate.

The best and most eflicient water-softening ingredients are the condensed polyphosphates, including the tripolyphosphates and the pyrophosphates. The detergent compositions of this invention can contain from 10 to 60% by weight sodium or p0 'um n hohates Other sequestering agents, ma erials such as ethylenediamine-tetracetic acid and alkali metal gluconates such as sodium gluconate, can also be employed in compositions of this invention, particularly in formulations for dairy use containing high percentages of caustic.

Polyphosphates have been shown to promote corrosion of certain metal parts of dishwashing machines but this corrosive effect can be overcome by including a relatively large proportion of a silicate in the composition. In this connection, metasilicate is important, not only from the standpoint of the machine itself, but also from the standpoint of the utensils washed. For instance, regardless of whether polyphosphate is present in a solution or not, highly alkaline dishwashing detergents containing no silicates can attack, etch, and darken aluminum utensils. Some of these formulations also have a destructive action on the over-the-glaze dish patterns. Suitable proportions of silicates in the formulation help overcome these difficulties.

Hence, the detergent compositions of this invention con- 2% 91 36 315 77 tain suificient chlorinated caustic to provide at least about 2M1- 'i' 'i' 0.5% available chlorine and as the principal detersive 24B 91 89 2 73 59 agent widely varying proportions of sodium or potassium polyphosphates, i.e., 10 to 60%; sodium or potassium silicates, i.e., 0 to 50%; sodium or potassium carbonates, The tormulatlons Shown in Table IV were made p Le 0 to 50%, sodium or potassium hydroxides, Le" 0 to with a product of this invention derived from sodium tri- 97%; and trisodium or tripotassium phosphate, i.e., 0 to Polyphosphate as the hygroscopic material, -r the P 50% Th amount f hl i t d caustic product di. uct of Example 7. Products of this invention derived narily constitutes about 3 to 75% by weight of the final from other complex sodium p p such as t so detergent composition, and for machine dishwashing dillm Py p p of Example 11, miXtureS o Comformulations, the chlorinated caustic product ordinarily P sodium Phosphates, can be Substituted the Product constitutes 10 to 50% by weight of the final formulation. 9 Example 7 in y of the formulations of Tab e IV Representative detergent compositions of this invention In e le 01 t Or in amounts generally described are shown in the following Table 111. These formula- Clsewhefe m the speclficatlofltions were prepared in duplicate using in the first instance Where the products of this invention are derived from the product of Example 7 which was retained on a 20 Sodium metasilicatei Such as in Example 10, the formulamesh screen (designated A) and in the second i t m tions shown in Table IV are altered correspondingly with product of Example 7 which passed through a 20 mesh respect'to complex sodium complex phosphate and sodium screen (designated B). Examples 12 through 19 are metasilicate content. Typical formulations wherein a suitable institutional type machine dishwashing detergents product of this invention derived from sodium metasilicate and Examples 20 through 7A are suitable glass dish procas the hygroscopic agent is employed are shown in the essing compounds for periodic use to remove tenacious following Table VI.

stains and food soils which tend to build up under many Table VI conditions when ordinary detergents are used.

Storage stability tests were performed with the formula- Example Number tions shown in Table IV. In these tests, about 10 gram mated-tents bY weight samples of the formulations were placed in small, clear 25 2s 27 as glass bottles closed with screw caps and the bottles were placed in a dark storage cabinet. A number of Product otlExam lo 10 1s 15 1o 20 such samples of each formulation were made up and the 283 3;} g g fi gj 22 g g} entire 10 gram sample used in the assay. The results gggiuglshHydr "g 10 5 appear in Table V below.

From these data it can be seen that formulations made sodmm Pymphosphm 13 from the larger particles were somewhat more stable with I claim: respest to loss of available chlorine Also, it pp that 1. A method for producing a stable, solid chlorinated dense soda ash decreases the stability of the product when caustic product containing up to about 18% available present m high proportions. chlorine which comprises intimately contacting a finely divided solid reaction mixture consisting essentially of sodium hydroxide and at least one hygroscopic material selected from the class consisting of sodium pyrophosphate, sodium tripolyphosphate and sodium metasilicate, the weight ratio of sodium hydroxide to hygroscopic material being about 1 to 9:1, with a gas stream containing sutficient chlorine to initiate an exothermic reaction, reacting the gas stream with the solid reaction mixture while maintaining a reaction temperature within the range from about 110 to 140 F. until the available chlorine content of the solid reaction mixture is about 8 to 18%, increasing the reaction temperature to about 135 to 160 F., maintaining the reaction temperature within the range from about 135 to 160 F. for a reaction period of at least about minutes but insuflicient to decrease the available chlorine content of the solid reaction mixture by more than about 2%, and cooling the solid reaction mixture, the finely divided solid reaction mixture being agitated throughout the reaction and subsequent cooling such that agglomeration does not occur.

2. A method for producing a stable, solid chlorinated caustic product containing up to about 18% available chlorine which comprises intimately contacting a finely divided solid reaction mixture consisting essentially of sodium hydroxide and sodium tripolyphosphate in a weight ratio of about 1.5 to 4:1 with a gas stream containing sufiicient chlorine to initiate an exothermic reaction, reacting the gas stream with the solid reaction mixture while maintaining a reaction temperature within the range from about 120 to 130 F. until the available chlorine content of the solid reaction mixture is about 8 to 18%, increasing the reaction temperature to about 140 to 150 F., maintaining the reaction temperature within the range from about 140 to 150 F. for a reaction period of at least about 10 minutes but insufficient to decrease the available chlorine content of the solid reaction mixture by more than about 2%, and cooling the solid reaction mixture, the finely divided solid reaction mixture being agitated throughout the reaction and subsequent cooling such that agglomeration does not occur.

3. A method for producing a stable, solid chlorinated caustic product containing up to about 18% available chlorine which comprises intimately contacting a finely divided solid reaction mixture consisting essentially of sodium hydroxide and sodium metasilicate in a weight ratio of about 1.5 to 4:1 with a gas stream containing sufiicient chlorine to initiate an exothermic reaction, reacting the gas stream with the solid reaction mixture while maintaining a reaction temperature within the range from about to F. until the available chlorine content of the solid reaction mixture is about 8 to 18%, increasing the reaction temperature to about to F., maintaining the reaction temperature within the range from about 140 to 150 F. for a reaction period of at least about 10 minutes but insuflicient to decrease the available chlorine content of the solid reaction mixture by more than about 2%, and cooling the solid reaction mixture, the finely divided solid reaction mixture being agitated throughout the reaction and subsequent cooling such that agglomeration does not occur.

4. The product produced by the process of claim 1.

5. The product produced by the process of claim 2.

6. A detergent composition consisting essentially of as the principal detersive agent an inorganic alkali metal detergent salt and sufficient to provide an available chlorine content of about 0.5% to 8% of the product of claim 1.

7. A machine dishwashing composition consisting essentially of at least one detergent salt wherein the cation is selected from the class consisting of sodium and potassium and the anion is selected from the class consisting of bicarbonate, carbonate, polyphosphate, orthophosphate, orthosilicate, metasilicate and hydroxide, and sufficient to provide an available chlorine content of about 0.5 to 8% of the product of claim 1.